Liquid crystal display device and manufacturing method thereof

ABSTRACT

A liquid crystal display device is provided having a plurality of electrodes in electrical communication with a conduction portion of a plurality of external wirings. An external portion is in electrical communication with the plurality of electrodes and comprises a conduction layer having a predetermined thickness, the conduction layer being arranged in a predetermined pattern on the external portion and between the external wirings and the external portion.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a liquid crystal display device and method ofmanufacturing it, and more particularly, relates to a structure of aconnection portion existing between a liquid crystal panel and aflexible substrate.

2. Description of the Related Art

There are various kinds of conventional liquid crystal display devices.In conventional liquid crystal display devices, by sealing a liquidcrystal layer between two transparent substrates, and applying a voltagebetween the electrodes having fixed pattern formed inside of thesubstrates, it is possible to display various images.

In many cases, conventional liquid crystal display have a flexiblesubstrate (referred to as an FPC hereinafter) to connect the liquidcrystal display panel to control and drive circuits located outside ofthe liquid crystal display device. An example of the liquid crystaldisplay device is described in the Utility Model (examined) PublicationHei 5-18789, (Japanese Utility Model (unexamined) Publication Hei2-87473).

The connection portions have a predetermined pitch (namely the space asbetween adjacent wirings) adapted to the pitch of the externalterminals, and the external terminals of the liquid crystal displaydevice and the connection portions of the FPC are electrically connectedto each other.

There are several methods to connect the FPC to the external terminals.One is to put the external terminals and other is to place ananisotropic conductive film between the external terminals and theconnection portions, then adhering them by applying heat and pressure.

In the latter method (heat seal method), the anisotropic conductive filmis formed on the surface of the connection portion of the flexiblesubstrate, and conductive particles are arranged at equal interval whichare made of a couple of μm fine metal particles, then so plating theconnection portion of the flexible substrate so as to contact to theexternal terminals. These heated components are pressed together so thatthe anisotropic conductive film is crushed and the external terminalsand the connection portions are electrically connected to each otherthrough the conductive particles. As mentioned above, the FPC is adheredto the liquid crystal panel easily by means of the anisotropicconductive film.

FIGS. 7, 8, 9, and 10 show an example of conventional technology usingthe heat seal method. FIG. 7 is a perspective view showing a connectionarea for connecting the FPC to the liquid crystal display panel, andFIG. 8 shows an enlarged cross-sectional view of an edge area of theliquid crystal display device. Typically transparent electrodes 3 areformed inside of a top substrate 1, and transparent electrodes 4 arealso formed inside of a bottom substrate. 2. A liquid crystal layer 5which is shown in FIG. 8 is sealed between top substrate 1 and bottomsubstrate 2, and a display area D is formed on the top substrate 1 asshown in FIG. 7. The bottom substrate extends outward beyond incomparison with the edge area of transparent substrate 1, and thisextended portion forms an electrode lead-out area 2a. External terminals3a, 4a are respectively connected to transparent electrodes 3, 4, whichare transparent, formed in the shape of stripes and are arranged inparallel on the electrode lead-out area 2a.

On the other hand, in a resin sheet of a FPC 10, a plurality ofconductive lines 12 are arranged almost in parallel, and the back sideof the edge area of the conductive line 12 is exposed at a connectionportion 10a of FPC 10. Connection portion 10a of FPC 10 is placed on theelectrode lead-out area 2a as mentioned above and then heated andcrimped. It is secured by the adhesive property of the anisotropicconductive film. As mentioned above, the external terminals 3a, 4a andthe conductive lines 12 are electrically connected each other.

FIG. 9 depicts a printed circuit board 30 on which a liquid crystaldrive circuit is mounted and connected to the liquid crystal displaydevice through FPC 10. The back side of the conductive lines 12 are alsoexposed at a connection portion 10b on a circuit board 30, and theexposed area is also covered by the anisotropic conductive film. In thesame way of above case, the connection portion 10b is secured to theprinting circuit board 30, and the edge area of the conductive line 12is conductivity connected to connection pads 31.

Conventional liquid crystal display devices have a number ofdisadvantages and problems as described below.

In the above mentioned conventional liquid crystal display device, whenthere is a transformation of the FPC, the stress caused by flexibilityof the FPC may be applied to the conductive connection portion which isbetween the external terminals and connection portion. As a result wiresmay be cut, separated, or cause an interruption in the circuit.Therefore, reliability of such electrical connections of the conductiveconnection portion is reduced.

Particularly, in the above mentioned case, the thickness of theconductive layer on external terminals 3a, 4a is between 200 Å and 600Å. This is a result of a process which the liquid crystal display deviceis manufactured, and this is much thinner than the thickness between 10μm or 40 μm which is the thickness of the connection pads 30 formed on aprinting circuit board 31. Therefore, in the case of crimping theanisotropic conductive film, the space between the FPC and peripheralportion of the external terminals is narrow, so the space where extraadhesive or/and conductive particles can escape is also narrow.Consequently, the contact area with the conductive particles in theanisotropic conductive film becomes much smaller than the connectionportion of the connection pads 31. As a result of this configuration,the resistance of the connection portion tends to increase, and the riskof a break in the circuit also increases. To improve this point, theremay be a way to form the anisotropic conductive film of connectionportion 10a so as to be thinner than connection portion 10b an so on.However, in this way, it is difficult to maintain the quality of theconnection portion, and there is a problem that the cost formanufacturing FPC 10 increase, therefore, the problem can not be solvedin the above way.

In addition, in so called heat seal method for connecting the FPCthrough the anisotropic conductive film, although it is an easieroperation for connecting, there is a problem, however, that due to thetemperature, the conductive particles float in the anisotropicconductive film. This results in the conductive particles beingseparated from upper surface of the external terminals, and theconductive connection between them are then easily broken.

Finally, in conventional devices, there is a tendency during themanufacturing process not to have a perfect alignment of arrangingconductive line 12 on external terminal 4a. FIG. 10 is an exploded viewof a single connection of line 12 on external terminal 4a. As showntherein, conductive line 12 is misaligned on external terminal 4a by anamount δ. This results in a smaller area of electrical contact, thusmaking a poorer contact having a high resistivity.

With the advent, in recent years, of large capacity size of liquidcrystal display devices, and the number of the external terminals hasincreased accordingly, thus resulting in the pitch between terminalsbeing very fine (which is a particular with requirement of small-sizeddevices). As such there has been an increase in defective products.

OBJECTS OF THE INVENTION

Therefore, it is an object of the present invention to overcome theaforementioned problems.

It is another object of the present invention to improve the reliabilityof electrical conductive connection between a liquid crystal panel andan FPC without increasing of cost for manufacturing.

It is a further object of this invention is to reduce the cost of liquidcrystal display device and products using it, and to improve thedurability of these products by improving the reliability of theelectrically conductive connection portion and the registration rate ofsuch products.

SUMMARY OF THE INVENTION

In accordance with an aspect of the present invention a liquid crystaldisplay device is provided with a liquid crystal panel having a liquidcrystal layer sealed between two substrates and an external terminalelectrically connected to an electrode used for applying an electricalfield to the liquid crystal layer. A flexible substrate includes aconnection portion electrically connected to the external terminal, anda conductive layer having a fixed thickness is provided in apredetermined pattern between the external terminal and the connectionportion.

In accordance with another aspect of the present invention a conductivelayer having a fixed thickness is provided in a predetermined patternbetween the external terminal, and the connection portion. Pressuresupplied from outside is transmitted intensively to the portion betweenthe external terminals and connection portions, and sufficient pressureis supplied to the portion between external terminal and connectionportion. As a connection area formed by the thickness of conductivelayer is attached to the connection portion, a contact area of aconductive adhesive provided between the external terminals and theconnection portion is broaden. This results in maintaining apredetermined conductivity. As a result, the occurrence of conductivedeterioration caused by stress or heat from outside is reduced. This isespecially true in the case when the external terminals and theconnection portion are electrically connected by sufficient pressure,when the flexible substrate is transformed along to the plane of by theconductive layer, and when contact pressure and the contact area isincreased.

In this case, the conductive layer should preferably be formed on asurface of the external terminal by arranging a stiffened conductivepaste in a predetermined pattern. In this way, it is easier to form theconductive layer.

The conductive paste should preferably be a conductive ink and theconductive layer should preferably be formed by printing. As such, theconductive layer can be formed in low cost.

Additionally, the conductive paste should preferably be formed using acarbon particle and a phenol resin as the main ingredient. In this case,electrical conductivity is sufficient, and making it possible to providethe conductive layer having certain conductivity without losing theconductive layer's shape. This results since the conductive layer isstiffened by heating concurrently with connection.

Furthermore, the upper side of the conductive layer should preferably beformed having a toughened or irregularly shaped surface. As such, aconductive contact area is broaden and the adhesion force becomestronger.

Additionally, an adhesive layer should preferably include conductiveparticles, which contact with the conductive layer, is formed betweenthe external terminal and the connection portion. An anisotropicconductivity can be obtained, and as the conductive particles in theadhesive comes in contact with the conductive layer, large contact areaand large compression force are obtained. In accordance with thisarrangement, and durability of the contact area for the stress and heatfrom out side are improved.

Furthermore, the conductive layer should preferably consist of samematerial with a conductive connection portion for connecting theelectrode of the liquid crystal panel and the external terminal. Assuch, the effect as mentioned above is obtained without adding otherfabrication steps.

In a method of manufacturing a liquid crystal display devices of theinvention, a conductive layer is formed in a predetermined pattern on asurface of an external terminal conductivity connected to an electrodefor applying an electric field to a liquid crystal layer containedbetween two substrates of a liquid crystal panel, and a connectionportion of a flexible substrate is electrically connected to theexternal terminal through the conductive layer. Especially, as theconductive layer is formed in a predetermined pattern on the externalterminal at the same time of forming with the same material as aconductive connection portion for connecting the electrode and theexternal terminals conductivity, it is not necessary to add furtherfabrication steps. The liquid crystal display device equipped with thisreliable connection portion between a liquid crystal panel and aflexible substrate can be obtained easily and at a low cost.

Additionally, it is preferable that the conductive layer is contactedonce to both of the two substrate, then eliminating a part of one of thesubstrates which contacts to the conductive layer, so that upper surfaceof the conductive layer which remains on other the substrate is formedroughened or irregular surface. In this way, when a substrate isremoved, upper portion of the conductive layer is separated with thesubstrate which is removed, therefore, it is possible to form thetoughened surface of upper side of the conductive layer which remains.As a result, this arrangement of the adhesion force is improved and thecontact area is increased.

Other objects and attainments together with a fuller understanding ofthe invention will become apparent and appreciated by referring to thefollowing description and claims taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings wherein like reference symbols refer to like parts.

FIG. 1 a perspective view of a liquid crystal display device inaccordance with an embodiment of the present invention;

FIG. 2 is an cross-sectional view showing a connection portion of aliquid crystal panel and a flexible substrate (FPC) of the embodiment ofFIG. 1;

FIG. 2A is an exploded view of the connection area of FIG. 2;

FIG. 3 is an enlarged cross-sectional view showing the externalterminals secured to the FPC of FIG. 1;

FIG. 4 is an enlarged cross-sectional showing the structure of the FPC;

FIG. 5 is a top view for showing the structure of the liquid crystaldisplay device of the embodiment of the present invention;

FIGS. 6A-6D are diagrams showing the process of forming the liquidcrystal display device in accordance with the present invention;

FIG. 7 is atop perspective view showing a conventional liquid crystaldisplay device;

FIG. 8 is a cross-sectional view showing a connection portion of aliquid crystal panel and a FPC of the conventional liquid crystaldisplay device;

FIG. 9 is another cross-sectional view of the conventional liquidcrystal display device;

FIGS. 10A and B are exploded perspective views of an external terminaland a conductive line in accordance with the conventional liquid crystaldisplay;

FIGS. 11A and B are exploded perspective views of an external terminaland a conductive line in accordance with the embodiment of FIG. 1; and

FIG. 12 is a plan view of FIG. 10B; and

FIG. 13 is a plan view of FIG. 11B.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Next, the embodiments of the invention will be explained with referencesto the drawings. Referring to FIGS. 1 and 2 the liquid crystal displaydevice of this embodiment is provided with top substrate 1 and bottomsubstrate 2 made of glass or a transparent resin substrate. Electrodes3, 4 which are preferably transparent, are formed in a striped shape ofan inner surface of the top substrate 1 and an inner surface bottomsubstrate 2. A liquid crystal layer 5 is then sealed between the topsubstrate 1 and bottom substrate 2 by seal material 6. A display area Dis formed at an outer portion of top substrate 1 corresponding to theliquid crystal layer 5. A refractor (not shown) may be provided on theouter portion of bottom substrate 2. Turning to FIG. 2, bottom substrate2 extends outwardly beyond substrate 1, forming an exposed electrodelead-out area 2a, on the inner surface of bottom substrate 2. Further,polarization plates (not shown) may be placed on the outer surface oftop substrate 1 and the outer surface of bottom substrate 2, in the caseof TN (Twisted Nematic) or STN (Super Twisted Nematic) type liquidcrystal display devices.

A plurality of external terminals 3a, 4a are aligned and formed on asurface of electrode lead-out area 2a. External terminals 3a, 4a arearranged at predetermined internals in a stripe shape. The externalterminals 3a are electrically connected to transparent electrodes 3 viaconductive connector portion 8 which are formed on the inner surface ofsubstrate 1, and external terminals 4a are electrically connected totransparent electrodes 4 which are formed on the inner surface ofsubstrate 2. On a surface of the electrode lead-out area 2a, aconnection portion 10a of flexible substrate 10 (FPC) is aligned andsecured to the position where the external terminals 3a, 4a are formed.

Referring specifically to FIG. 2A, FPC 10 is provided with a resin sheet11 which is transparent, and conductive lines 12 made of carbon layerformed on the inner of surface resin sheet 11, (conductive lines 12) arepreferably being arranged in parallel. Referring to FIGS. 3 and 4, FPC10 further comprises an anisotropic conductive film 13 and a coat layer14 for covering a portion other than the connection portion 10a.Anisotropic conductive film 13 is provided with adhesive materials madeof preferably a thermoplastic resin having conductive particles 13b.Conductive particles 13b consist of small carbon particles or metallicparticles which are arranged in at predetermined intervals.

As shown in FIGS. 1 and 2, on external terminals 3a, 4a which arrangedon a surface electrode lead-out area 2a, two circular shaped conductivelayers 7 are aligned in the direction where external terminals 3a, 4aare extended on electrode lead-out area 2a. External terminals 3a, 4aand conductive lines 12 are electrically connected through theanisotropic conductive film 13 sandwiching the conductive layer 7.

Conductive lines 12 are secured to external terminals 3a, 4a as follows.The adhesive material of anisotropic film 13 is melted by applying heatand applying pressure on conductive lines 12 and external terminals 3a,4a. After anisotropic film 13 has solidified conductive layer 7 is thussecured to conductive line 12, provided secure mechanical and electricalconnections.

FIG. 5 is a top perspective view of the present embodiment. Externalterminals 3a are electrically connected to transparent electrodes 3(FIG. 2) through conductive connection portion 8 formed by same materialof conductive layer 7. Further, external terminals 4a are electricallyconnected to transparent electrodes 4 (FIG. 2) formed on the surface ofbottom substrate 2. The number and arrangement of external terminals 3aand 4a are defined according to the pattern of transparent electrodes 3,4 formed on top and bottom sides of liquid crystal layer 5. Conductivelayer 7 is formed in a predetermined pattern on external lead-out area2a.

FIGS. 6A-6D show a process of fabricating the liquid crystal displaydevice in accordance with the present invention. As shown in FIG. 6A,external terminals 3a, 4a and transparent electrode 4 are formed in apredetermined pattern on a surface of bottom substrate 2. Seal material60 is secured and arranged surrounding the display area. Further,conductive connection pattern 80 to electrically connect top and bottomsubstrates is formed on external terminals 3a, and a conductive layerpattern 70 is formed on external terminals 3a and 4a by, for example,screen printing using conductive ink. Such conductive ink typicallycomprises carbon particles dispersed in a phenol resin. The shape ofconductive layer pattern 70 is a column having a diameter between 0.2 mmand 0.5 mm, which is approximately same as width of the externalterminal 3a, 4a and having a thickness of approximately 30 mm.

Next, as shown in FIG. 6B, transparent electrode 3 having apredetermined pattern is formed on top substrate 1. Then seal material60, conductive layer pattern 70 and connection pattern 80, forconnecting transparent electrodes 3 and to external electrodes 3a aresecured on the inner surface of top substrate 1. Substrate 1 andsubstrate 2 are secured by heating at the temperature range of 150° C.to 200° C., and adhering seal material 60, conductive layer pattern 70and conductive connection pattern 80 between the inner surface of topsubstrate 1 and the inner surface of bottom substrate 2. Thereafter sealmaterial 60 is completely hardened for forming seal portion 6. Topsubstrate 1 and bottom substrate 2 are secured to each of them by sealportion 6, and conductive layer pattern 70 and conductive connectionpattern 80 are secured to the inner surface of top substrate 1 and theinner surface of bottom substrate 2. It is noted that contact portionbetween substrates 1 and 2 is stiffened periodically. The characteristicof stiffness of conductive layer pattern 70 and conductive connectionpattern 80 can be regulated by selecting suitable materials or addingadditional stiffening agents, such as a polymerization inhibitor to varythe stiffness characteristics of seal material 60.

Referring to FIG. 6B, top substrate 1 and bottom substrate 2 are cutinto individual liquid crystal panels, along lines P1 and P2.Additionally, as shown in FIGS. 6C and 6D, a portion of top substrate 1is eliminated to form electrode lead-out area 2a along line P4.Conductive layer pattern 70 is divided near the middle of the conductivelayer 7 when eliminating the part of top substrate 1. Conductive layer 7is formed having a roughened or irregular upper surface 7a. In thepreferred embodiment, the thickness of conductive layer 7 isapproximately between 10 μm and 20 μm. Finally, the device is trimmedalong line P3.

As noted above liquid crystal layer 5 is formed by sealing liquidcrystal inside of seal portion 6 and securing the FPC 10 shown in FIG. 4on electrode lead-out area 2a. Conductive layer 12 of FPC 10 is arrangedon electrode lead-out area 2a in electrical connection withcorresponding external terminals 3a, 4a. FPC 10 is preferably connectedto the liquid crystal panel by heat sealing using a heat crimping toolfor applying heat and pressure.

The conditions of this heat sealing process is, in general, at atemperature range between 130° C. and 150° C. at the surface of pressingside, having a pressure range between 20 kg/cm³ and 30 kg/cm³, and for atime between 5 sec. and 10 sec. It is very important to control theabove-discussed conditions, since these conditions can contribute to thereliability of the connection between the liquid crystal panel and FPC10.

Turning again to FIG. 4, in the case that conductive layer 7 is notformed as in the conventional devices, when the temperature, pressure,and time are lower than the preferred range for heat sealing asmentioned above, the adhesion force tends to deteriorate because ofinadequate fusion of the adhesive material 13a. Moreover, when thetemperature, pressing force and the time are higher than the range ofthe conditions for heat sealing mentioned above, there is also atendency of poor connections because conductive particles 13b float inthe adhesive material 13a without making adequate contact, by theheating of the anisotropic film 13.

In the present embodiment, it is also preferable for heat sealing in therange of the condition between 100° C. to 180° C., at the pressurebetween 15 kg/cm³ to 50 kg/cm³, and at a time between 5 sec. to 10 sec,it would be possible to manufacture the device without causing anyproblems conductive connection portion.

A liquid crystal display devices constructed in accordance with thepresent invention having a pitch for the external terminals 3a, 4abetween 0.8 mm and 0.4 mm is reliable and does not exhibit thedisadvantages and draw-backs of conventional liquid crystal displays.

A liquid crystal display that is heat sealed as mentioned above,adhesive materials 13a of the anisotropic conductive film are meltedonce, then hardened such that both of conductive line 12 and externalterminals 3a, 4a are in contact with conductive particles 13b. At thistime, upper surface of the conductive layer 7 formed on the externalterminals 3a, 4a form an electrode lead-out area 2a so that the uppersurface of conductive layer 7 and conductive lines 12 are secured asshown in FIG. 3 to provide a reliable electrically conductiveconnection. Also, according to the present invention there is anadvantage that the contact area with conductive particles in theanisotropic conductive film can be widened, to a space where theanisotropic conductive film can be released and secured by the thicknessof the conductive layer 7 as compared to. However, at this time, becauseof over heating of heat seal 6, conductive layer 7 is hardened forsecuring its shape and therefore, conductive layer 7 does not lose itsshape.

In general, external terminals 3a, 4a are made of thin metal film,however, electrode lead-out area 2a are formed having a thicknessapproximately between 2000 Å to 3000 Å. As noted above in conventionaldevices due to misalignment during the manufacturing process if any,there is length δ of conductive line 12 that is not in contact withexternal terminal 4a, as shown in FIGS. 10A and B and 12. This resultsin a connection that has a high resistivity and is less mechanicallysecured. However, in the present embodiment, as shown in FIGS. 11A and Band 13, if there is any misalignment of the conductive line 12 with theexternal terminal 3a, the portion of conductive line 12 would be incontact with a side wall of conductive layer 7. This arrangementprovides for a good electrical having a lower resistivity thanconventional devices. Moreover, there is increased mechanical strength.As presently preferred, the thickness of conductive layer 7 is in therange of 10 μm to 20 μm even the case which the electrode lead-out area2a is rather thick.

In conventional devices a length x of conductive line 12 is in contactwith external terminal 4a as shown in FIG. 8. This length x correspondsto a certain resistivity. Now referring to FIG. 2A; the length ofcontact of conductive line 12 is in the sum of the contact areaa+b+c+d+e+f+g+h+i which is greater than length x of the conventionaldevice. By virtue of this feature, resistivity is reduced and mechanicalstrength is increased.

Additionally, as upper surface 7a of the conductive layer 7 is formedhaving a roughened surface, thus, adhesion force between the uppersurface 7a of the conductive layer 7 and the anisotropic film 13 isimproved. As conductive particles 13b are rigidly connected to uppersurface 7a, positive electrical connection is achieved. In accordancewith this structure, durability and heat resistance of the device areimproved.

In the preferred embodiment, the liquid crystal panel and FPC areadhered by hot adhesion through the anisotropic film 13. However, aslong as there is a face to face connection, other techniques such aswelding by pasting conductive paste, solder, reflow, or the like or canobtained similar advantages.

Further, FC 10 is not limited to an FPC having only wiring, variouskinds of the FPC can be employed, such as FPC mounting semiconductordevices and the like.

In this embodiment, carbon lines forming conductive layer 7, conductiveconnection portion 8 which are made of the same material with conductiveink are formed, adhesion and conductivity between the FPC and theconductive layer formed on the external terminals are thus excellent. Byusing carbon particles as conductive particles aligned in theanisotropic conductive film, further improvement of conductivity can beachieved.

As mentioned above, as conductive layer 7 is formed at the same time andof the same material, it is possible to form the layer without changingthe manufacturing process or adding steps. However, needless to say, theconductive layer 7 can be formed in a separate process after forming theelectrode lead-out area 2a.

The conductive layer can not only have a circular shape but can beformed in other shapes such as a rectangle. It is preferable to form theconductive layer in circle or in dotted shape having substantially thesame width with the external terminals are aligned along to thedirection of the external terminals.

As explained above, the invention provides the following effects.

According to an aspect of the present invention, as a conductive layerhaving a fixed thickness and partially formed between the externalterminal and the connection portion, external pressure supplied istransmitted intensively to the portion between external terminals andconnection portions, and sufficient pressure is supplied to the portionbetween externals terminal and connection portion, and as the connectionformed by the thickness of conductive layer is attached to the portion.The contact area of conductive adhesive formed between the externalterminals and connection portion are broaden and the good electricalconductivity is kept and maintained. As a result of it, the occurrenceof poor conductivity caused by suffering stress or heat from out side isreduced. A device constructed in accordance with the present inventionprovides a secure mechanical and electrical connection even when theflexible substrate is transformed.

In accordance with another aspect of the present invention by arrangingand stiffening a conductive paste in a predetermined pattern, it makeseasy to form the conductive layer. Moreover, the conductive layer can beformed in low cost by a printing process.

In this arrangement since conductivity is satisfied, and it is possibleto make the conductive layer having certain conductivity without losingthe conductive layer's shape, because it is possible to stiffen it byheating concurrently with connection of the conductive line. Theconductive layer as forming irregularly the surface of the conductivelayer, a conductive contact area is broaden and adhesion force becomestrong.

In accordance with an additional aspect of the present invention, ananisotropic conductivity can be obtained, and as the conductiveparticles in the adhesive contacts the conductive layer, a large contactarea and a large compression force are obtained, and durability of thecontact area for the stress and heat from out side are improved.

As noted above, as the conductive layer consists of the same materialwith the conductive connection portion for connecting the electrode ofthe liquid crystal panel and the external terminal. This results in notincreasing the number of manufacturing steps.

As the conductive layer is formed in a predetermined pattern on theexternal terminal at the same time of forming with and formed by thesame material the conductive connection portion it is not necessary toadd further steps of process, and the liquid crystal display device canbe obtained easily and in low cost.

It is preferable for the upper surface of the conductive layer to beroughened or irregularly shaped. As a result of this feature,improvement of the adhesion force and an increase of the contact areacan be achieved.

Wile conductive layer 7 is preferably formed in a predetermined pattern,one of ordinary skill in the art would appreciate that is could also beformed in a random pattern.

While the invention has been described in conjunction with severalspecific embodiments, it is evident to those skilled in the art thatmany further alternatives, modifications and variations will be apparentin light of the foregoing description. Thus, the invention describedherein is intended to embrace all such alternatives, modifications,applications and variations as may fall within the spirit and scope ofthe appended claims.

Reference Symbols

1: Top substrate

2: Bottom substrate

2a: Electrode lead-out area

3,4: Electrodes which are transparent

3a,4a: External terminals

7: Conductive layer

7a: Upper surface

8: Conductive connection portion

10: FPC

12: Conductive lines

13: Anisotropic conductive film

13a: Adhesive

13b: Conductive particles

What is claimed is:
 1. A liquid crystal display device having first andsecond substrates, a plurality of first electrodes arranged on the firstsubstrate, and a plurality of second electrodes arranged on the secondsubstrate, comprising: an external portion arranged on the firstsubstrate in electrical communication with the plurality of firstelectrodes; a conductive layer comprising a first material and beingarranged in a pattern on said external portion; and a conductiveconnection portion positioned between the first and second substratesand comprising the first material for electrically connecting theplurality of second electrodes to said external portion, the pluralityof first and second electrodes being in electrical communication with aconnection portion of a plurality of external wirings via said externalportion.
 2. A liquid crystal display device according to claim 1,wherein said external portion comprises a plurality of externalterminals, and wherein said conductive layer is formed on a surface ofsaid external terminals by arranging a stiffened conductive paste in apredetermined pattern.
 3. A liquid crystal display device according toclaim 2, wherein said conductive paste comprises a conductive ink andsaid conductive layer is formed by printing.
 4. A liquid crystal displaydevice according to claim 2, wherein said conductive paste comprisescarbon particles and a phenol resin.
 5. A liquid crystal display deviceaccording to claims 2, wherein an upper side of said conductive layercomprises a roughened surface.
 6. A liquid crystal display deviceaccording to claim 2, further comprising an adhesive layer including aconductive particle in contact with said conductive layer, said adhesivelayer being formed between said external terminal and the connectionportion of the plurality of external wirings wherein the adhesive layeris disposed between the conductive layer and the external wirings.
 7. Aliquid crystal display device according to claim 1, wherein the externalwirings comprise a flexible substrate.
 8. A liquid crystal displaydevice according to claim 1, wherein said conductive layer comprises amaterial comprising an electrically conductive connection portion forelectrically connecting the plurality of electrodes with the externalwirings.
 9. A liquid crystal display device having a plurality ofelectrodes in electrical communication with a connection portion of aplurality of external wirings comprising: an external portion inelectrical communication with the plurality of electrodes; a conductivelayer formed in a pattern on a surface of said external portion; and anadhesive layer including a conductive particle in contact with saidconductive layer, said adhesive layer being formed between said externalportion and the connection portion of the plurality of external wirings,wherein the adhesive layer is disposed between the conductive layer andthe external wirings.
 10. A method of manufacturing a liquid crystaldisplay device having a plurality of electrodes in electricalcommunication with a connection portion of a plurality of externalwirings; said method comprising the steps of: providing the first andsecond substrates; forming an external portion in electricalcommunication with the plurality of electrodes; forming a conductivelayer comprising a first material arranged in a pattern on a surface ofthe external portion and sandwiching the conductive layer so that theconductive layer is in contact with the first and second substrates;forming a conductive connection portion comprising the first material,positioned between first and second substrates and formed substantiallysimultaneously with the conductive layer; removing a portion of thesecond substrate in an area which contacts the conductive layer, so thatan upper surface of the conductive layer is formed having a roughenedsurface; and electrically connecting the connection portion to theexternal portion via the conductive layer.
 11. A method of manufacturinga liquid crystal display device having a plurality of electrodes onfirst and second substrates in electrical communication with aconnection portion of a plurality of external wirings, said methodcomprising the steps of: forming an external portion on the firstsubstrate in electrical communication with the plurality of electrodes;forming a conductive layer in a pattern on a surface of the externalportion; forming a conductive connection portion positioned between thefirst and second substrates; forming an adhesive layer, including aconductive particle in contact with the conductive layer, between theexternal portion and the connection portion of the plurality of externalwirings, wherein the adhesive layer is disposed between the conductivelayer and the external wirings; and electrically connecting theconnection portion to the external portion via the conductive layer. 12.A method of manufacturing a liquid crystal display device having firstand second substrates, a plurality of first electrodes being arranged onthe first substrate and a plurality of second electrodes arranged on thesecond substrate, said method comprising the steps of: forming anexternal portion on the first substrate in electrical communication withthe plurality of first electrodes; forming a conductive layer comprisinga first material in a pattern on a surface of the external portion; andforming a conductive connection portion comprising the first materialbetween the first and second substrates for electrically connecting theplurality of second electrodes to said external portion, wherein theplurality of first and second electrodes are in electrical communicationwith a connection portion of a plurality of external wirings via theexternal portion.
 13. A method of manufacturing a liquid crystal displaydevice having a plurality of electrodes in electrical communication withthe connection portion of a plurality of external wirings, said methodcomprising the steps of: providing first and second substrates; formingan external portion on the first substrate in electrical communicationwith the plurality of electrodes; forming a conductive layer in apattern on a surface of the external portion and sandwiching theconductive layer so that the conductive layer is in contact with thefirst and second substrates; removing a portion of the second substratein an area which contacts the conductive layer, so that an upper surfaceof the conductive layer is formed having a roughened surface; andelectrically connecting the connection portion to the external portionvia the conductive layer.